1. Field of the Invention
The present invention relates to a vapor compression refrigerator having a Rankine cycle, for recovering power, utilizing the waste heat of a heat generating device and a hot-gas cycle capable of heating the heat generating device, effectively applicable to an automotive climate control system mounted on a vehicle and having an auxiliary heating function adapted to help increase the engine water temperature to secure a comfortable temperature of the passenger compartment within a short period of time, from the time of starting the heating operation, when the engine water temperature is low.
2. Description of the Related Art
In a conventional vapor compression refrigerator disclosed in Japanese Patent Publication No. 2540738, for example, a component part (condenser) of a refrigeration cycle is shared to form a Rankine cycle, the waste heat of the vehicle engine (heat generating device) is recovered as power by an expander doubling as a compressor and the power thus recovered is applied to the engine.
The engine waste heat is supplied to the heater in a heater circuit and, thus, is used as a heat source for the operation of heating the passenger compartment (hereinafter referred to simply as the heating operation).
In the hybrid car of which the ownership has recently begun to increase, rate of operation of the engine at a low vehicle speed is set to a low level. Thus, heat (waste heat) generated by the engine is very small in amount. Especially in winter, a sufficient amount of heat cannot be supplied as a heat source for the heater. In the hybrid car, therefore, the engine is required to run to secure the heat source for the heater even while the vehicle is driven at low speed at the sacrifice of a low fuel consumption efficiency.
In ordinary vehicles, on the other hand, the recently improved engine efficiency has reduced the waste heat generated by cooling the engine, thereby posing a problem, as in the hybrid car, that the heat source for the heater is insufficient. To compensate for the heat source shortage, ordinary vehicles carry an exclusive PTC heater, for example, in spite of an increased cost.
In view of this, there has been proposed a system in which the compressor, the condenser and the heater in the refrigeration cycle and the Rankine cycle are utilized, and by adding a restricting portion between the heater and the condenser, a heat pump cycle (through the compressor, the heater, the restricting portion and the condenser in that order) is formed so that the condenser exhibits the heat absorption function while the engine warm-up is promoted by the heating function of the heater.
In the case where the atmospheric temperature is very low (−10° C. or lower, for example), however, the heat absorption of the condenser from the atmosphere as a heat pump cycle requires that the temperature of the refrigerant flowing in the condenser must be reduced below the atmospheric temperature. That is to say, the refrigerant pressure is required to be reduced, so that the pressure difference between the suction side and the discharge side of the compressor is greatly increased, thereby considerably reducing the refrigerant flow rate. This poses the problem that the heating ability of the heater cannot be sufficiently exhibited.
In a conventional vehicle carrying a water-cooled engine, on the other hand, the engine cooling water is used as a heat source of the heating operation. In the case where the heating operation is started while the cooling water temperature is still low at the time of starting the engine, however, air not sufficiently heated would be blown into the passenger compartment and the occupants would feel uncomfortable. In the conventional automotive climate control system, therefore, the operation of the blower and the refrigeration cycle is suspended to prevent the cold air from being blown out (engine warm-up control operation) while the cooling water is not higher than a predetermined temperature.
An electric vehicle incapable of using the engine cooling water for the heating operation, on the other hand, is often equipped with a heat pump air conditioning system as described in Japanese Unexamined Patent Publication No. 8-216655. In such a system, for example, the heating operation is performed using the hot water heated by a high-pressure (high-temperature) refrigerant as a heat source (or using a high-pressure refrigerant as a heat source). Also, in this electric vehicle, as in the engine-driven vehicle, the engine warm-up control operation is performed by preventing the cold air from being blown out before the heat source (hot water, refrigerant) reaches a predetermined temperature.
In a system using a heat pump cycle disclosed in Japanese Unexamined Patent Publication No. 8-216655, as shown in FIG. 13, during the operation of cooling the passenger compartment (hereinafter referred to simply as the cooling operation), the refrigerant is discharged from a refrigerant compressor 1 and by switching a solenoid valve, introduced into the refrigerant compressor 1 again through a water-refrigerant heat exchanger 2, an outer heat exchanger (acting as a condenser) 4 and an inner heat exchanger (evaporator) 6 in that order. During the heating operation, on the other hand, the solenoid valve is switched so that the refrigerant discharged from the refrigerant compressor 1 is sucked into the refrigerant compressor 1 again through the water-refrigerant heat exchanger 2 and the outer heat exchanger (acting as an evaporator) 4 in that order. Further, during the dehumidifying operation, the solenoid valve is so switched that the refrigerant discharged from the refrigerant compressor 1 is sucked again into the refrigerant compressor 1 through the water-refrigerant heat exchanger 2, the outer heat exchanger (acting as a condenser) 4 and the inner heat exchanger (evaporator) 6 in that order. In this way, with the system using the heat pump cycle, the heat pump is operated using the water-refrigerant heat exchanger and the condenser or the evaporator in all operation modes. Reference numeral 13 designates a combustion heater used as an auxiliary heater when the atmospheric temperature is so low that the water-refrigerant heat exchanger 2 alone cannot sufficiently heat the water. Numeral 10 designates a heater core using hot water.
In the heat-pump type air conditioning system mounted on the electric vehicle described in Japanese Unexamined Patent Publication No. 8-216655, however, the amount of heat absorbed into the outer heat exchanger (acting as an evaporator) is decreased with a decrease in the atmospheric temperature and, therefore, the high-pressure refrigerant drops in temperature. The system using the heat pump cycle, therefore, cannot be used in an environment such as cold areas in the winter season.
Japanese Patent Publication No. 3237187, on the other hand, discloses an automotive climate control system using a hot gas heater system that can work even in cold areas. In the cooling operation, as shown in FIG. 14, the solenoid valve of this hot gas heater system is switched so that the refrigerant discharged from the refrigerant compressor 1, after cooling the air through the outer heat exchanger (condenser) 4 and the inner heat exchanger (evaporator) 6, is sucked into the refrigerant compressor 1. During the heating operation, on the other hand, the solenoid valve is switched so that the refrigerant discharged from the refrigerant compressor 1, by bypassing the outer heat exchanger 4, directly enters the inner heat exchanger (acting as a heat-emitter) 6, and after heating the air, is sucked into the refrigerant compressor 1. This inner heat exchanger 6 is arranged in the air flow upstream of the heater core 10 using the cooling water of the engine 11 and works as an auxiliary heating function.
In the conventional automotive climate control system using a hot-gas heater system described above, however, the inner heat exchanger 6 functioning as an evaporator providing a low-pressure-side heat absorber during the cooling operation functions as a high-pressure-side heat emitter during the heating operation. The condensed water, the frost, etc. generated in the inner heat exchanger 6 during the cooling operation is heated and evaporated during the heating operation, and the resultant vapor is liable to be blown against and fog the window glass.